Vapor Pressure Isotope Effects in Halogenated Organic Compounds and Alcohols Dissolved in Water
Why this work is in the frame
A frame that forgets how it found something cannot be audited. These are the routes that admitted this work.
Bibliographic record
Abstract
Volatilization causes changes in the isotopic composition of organic compounds as a result of different vapor pressures of molecules containing heavy and light isotopes. Both normal and inverse vapor pressure isotope effects (VPIE) have been observed, depending on molecular interactions in the liquid phase and the investigated element. Previous studies have focused mostly on pure compound volatilization or on compounds dissolved in organic liquids. Environmentally relevant scenarios, such as isotope fractionation during volatilization of organics from open water surfaces, have largely been neglected. In the current study, open-system volatilization experiments (focusing thereby on kinetic/-nonequilibrium effects) were carried out at ambient temperatures for trichloromethane, trichloroethene, trichlorofluoromethane, trichlorotrifluoroethane, methanol, and ethanol dissolved in water and, if not previously reported in the literature for these compounds, for volatilization from pure liquids. Stable carbon isotopic signatures were measured using continuous flow isotope ratio mass spectrometry. The results demonstrate that volatilization of the four halogenated compounds from water does not cause a measurable change in the carbon isotopic composition, whereas for pure-phase evaporation, significant inverse isotope effects are consistently observed (+0.3 ‰< ε < + 1.7 ‰). In contrast, methanol and ethanol showed normal isotope effects for evaporation of pure organic liquids (-3.9 ‰ and -1.9 ‰) and for volatilization of compounds dissolved in water (-4.4 ‰ and -2.9 ‰), respectively. This absence of measurable carbon isotope fractionation considerably facilitates the application of isotopic techniques for extraction of field samples and preconcentration of organohalogens-known to be important pollutants in groundwater and in the atmosphere.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it